A battery cell, a battery and an electric device

Abstract

The application provides a battery monomer, a battery and a power utilization device, and belongs to the technical field of batteries. The battery monomer comprises a negative electrode sheet, the negative electrode sheet comprises a main body part and a tab, the main body part has opposite first and second ends, the tab is arranged at the first end, the direction extending from the first end to the second end is the width direction of the negative electrode sheet, the main body part comprises a first region, a second region and a third region which are sequentially distributed along the width direction, the ion diffusion coefficient of the first region is greater than that of the second region, and / or the ion diffusion coefficient of the third region is greater than that of the second region. The battery monomer of the application can reduce the kinetic performance of the middle region of the negative electrode sheet, can improve the kinetic performance of the end region of the negative electrode sheet, can further offset or weaken the problem of uneven polarization of different regions in the cycle process of the battery monomer, can improve the lithium precipitation problem or sodium precipitation problem of the negative electrode sheet, and can improve the service life of the battery monomer.

Description

Technical Field

[0001] This application relates to the field of battery technology, and in particular to a battery cell, a battery, and an electrical device. Background Technology

[0002] In recent years, with the increasingly widespread application of lithium-ion batteries, they have been widely used in energy storage power systems such as hydropower, thermal power, wind power, and solar power plants, as well as in power tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, aerospace, and many other fields. Due to the significant advancements in lithium-ion battery technology, higher requirements have been placed on its energy density, cycle performance, and safety performance.

[0003] As lithium batteries continue to develop towards higher power and higher energy density, capacity decay has become the main limiting factor for lithium batteries. Summary of the Invention

[0004] This application is made in view of the above-mentioned problems, and its purpose is to provide a battery cell, a battery and an electrical device that can slow down the capacity decay of the battery cell and improve the service life of the battery cell.

[0005] To achieve the above objectives, a first aspect of this application provides a battery cell comprising an electrode assembly, the electrode assembly including a negative electrode sheet, the negative electrode sheet including a body portion and a tab, the body portion having a first end and a second end opposite to each other, the tab being disposed at the first end, the direction extending from the first end to the second end being the width direction of the negative electrode sheet, the body portion including a first region, a second region and a third region sequentially distributed along the width direction, the ion diffusion coefficient of the first region being greater than the ion diffusion coefficient of the second region, and / or the ion diffusion coefficient of the third region being greater than the ion diffusion coefficient of the second region; the ion diffusion coefficient includes the lithium ion diffusion coefficient or the sodium ion diffusion coefficient.

[0006] Therefore, the battery cell of this application divides the main body into a first region, a second region, and a third region distributed sequentially along the width direction. The lithium-ion diffusion coefficient or sodium-ion diffusion coefficient of the first region is greater than that of the second region, and / or the ion diffusion coefficient of the third region is greater than that of the second region. The second region is closer to the center of the negative electrode sheet than the first and third regions. This reduces the kinetic performance of the central region of the negative electrode sheet, i.e., slows down the migration and diffusion of lithium ions or sodium ions in the central region of the negative electrode sheet, increases the polarization of the central region of the negative electrode sheet, and improves the kinetic performance of the end region of the negative electrode sheet, i.e., accelerates the migration and diffusion of lithium ions or sodium ions in the end region of the negative electrode sheet, reduces the polarization of the end region of the negative electrode sheet. This counteracts or weakens the problem of uneven polarization in different regions during battery cell cycling, improves the lithium or sodium deposition problem of the negative electrode sheet and the capacity decay of the battery cell, and increases the service life of the battery cell.

[0007] In any embodiment, the ratio of the lithium-ion diffusion coefficient of the first region to the lithium-ion diffusion coefficient of the second region is 2 to 1000, and / or the ratio of the lithium-ion diffusion coefficient of the third region to the lithium-ion diffusion coefficient of the second region is 2 to 1000. By ensuring that the ratio of the lithium-ion diffusion coefficient of the first region to the lithium-ion diffusion coefficient of the second region and / or the ratio of the lithium-ion diffusion coefficient of the third region to the lithium-ion diffusion coefficient of the second region are within the above ranges, the problem of accelerated lithium deposition in the middle of the battery cell and accelerated capacity decay in the later stages of cycling can be avoided or improved due to the excessively high kinetic performance of the first region and / or the third region located at the ends and the excessively low kinetic performance of the second region located in the middle.

[0008] In any embodiment, the main body is divided into a first region, a second region, and a third region sequentially along its width. The ratio of the lithium-ion diffusion coefficient in the first region and / or the third region to the lithium-ion diffusion coefficient in the second region is 5 to 500. When the main body is divided into a first region, a second region, and a third region sequentially along its width, by ensuring that the ratio of the lithium-ion diffusion coefficient in the first region to the lithium-ion diffusion coefficient in the second region and / or the ratio of the lithium-ion diffusion coefficient in the third region to the lithium-ion diffusion coefficient in the second region is within the above range, the problem of accelerated lithium deposition in the middle of the battery cell due to excessively high kinetic performance in the first region and / or the third region at the ends and excessively low kinetic performance in the second region in the middle can be avoided or improved.

[0009] In any embodiment, the lithium-ion diffusion coefficient located in the first region and / or the third region is 10. -9 cm 2 / s~10 -11cm 2 / s, the lithium-ion diffusion coefficient in the second region is 10. -11 cm 2 / s~10 -12 cm 2 / s. By ensuring that the lithium-ion diffusion coefficients in the first region and / or the third region, as well as the second region, are within the aforementioned range, it is beneficial to reduce the kinetic performance of the central region of the negative electrode, increase the polarization of the central region of the negative electrode, and improve the kinetic performance of the end region of the negative electrode, thereby reducing the polarization of the end region of the negative electrode.

[0010] In any embodiment, the area of ​​the second region accounts for 50% to 70% of the total area of ​​the main body. By making the proportion of the area of ​​the second region within the above range, the area sizes of the first and third regions can be further divided according to the polarization of the negative electrode sheet during the cycle of the battery cell. This allows for more precise offsetting or reduction of the problem of uneven polarization in different regions during the cycle of the battery cell, improving the capacity decay of the battery cell and increasing its service life.

[0011] In any embodiment, the aspect ratio of the first region, the second region, and the third region along the width direction is 15%–25%: 50%–70%: 15%–25%. By ensuring that the aspect ratio of the first region, the second region, and the third region along the width direction is within the above range, it is advantageous to divide the first region, the third region, and the second region located at the two ends according to the polarization of the negative electrode sheet during the battery cell cycle. This allows for more precise offsetting or reduction of the problem of uneven polarization in different regions during battery cell cycle, improving the capacity decay of the battery cell, and increasing the service life of the battery cell.

[0012] In any embodiment, the negative electrode sheet includes a negative electrode active material layer, which includes a negative electrode active material. The ion diffusion coefficient of the negative electrode active material located in the first region and / or the third region is greater than that of the negative electrode active material located in the second region. The battery cell of this application, by making the lithium-ion diffusion coefficient or sodium-ion diffusion coefficient of the negative electrode active material located in the first region and / or the third region greater than that of the negative electrode active material located in the second region, can reduce the kinetic performance of the central region of the negative electrode sheet, increase the polarization of the central region of the negative electrode sheet, and improve the kinetic performance of the end region of the negative electrode sheet, reducing the polarization of the end region of the negative electrode sheet. This counteracts or weakens the problem of uneven polarization in different regions during battery cell cycling, improves the lithium or sodium plating problem of the negative electrode sheet and the capacity decay of the battery cell, and increases the service life of the battery cell.

[0013] In any embodiment, the negative electrode sheet includes a negative electrode active material layer, and the first region, the second region, and the third region include the same conductive agent. Based on the mass of the negative electrode active material layer in the first region, the mass percentage of the conductive agent in the negative electrode active material layer in the first region is W1. Based on the mass of the negative electrode active material layer in the second region, the mass percentage of the conductive agent in the negative electrode active material layer in the second region is W2. Based on the mass of the negative electrode active material layer in the third region, the mass percentage of the conductive agent in the negative electrode active material layer in the third region is W3, where W1 < W2 and / or W3 < W2. When the conductive agent used in the first, second, and third regions is the same, the battery cell of this application can reduce the kinetic performance of the middle region of the negative electrode sheet by making the mass ratio of the conductive agent in the negative electrode active material layer in the second region greater than that in the negative electrode active material layer in the first and / or third regions. This reduces the migration and diffusion of lithium ions or sodium ions in the middle region of the negative electrode sheet, increases the polarization of the middle region of the negative electrode sheet, and improves the kinetic performance of the end region of the negative electrode sheet. This accelerates the migration and diffusion of lithium ions or sodium ions in the end region of the negative electrode sheet, reduces the polarization of the end region of the negative electrode sheet, and thus offsets or weakens the problem of uneven polarization in different regions during battery cell cycling, improves the lithium or sodium plating problem of the negative electrode sheet and the capacity decay of the battery cell, and improves the service life of the battery cell.

[0014] In any embodiment, the difference between W2 and W1 is 0.5wt% to 2wt%, and / or the difference between W2 and W3 is 0.5wt% to 2wt%. By ensuring that the difference between the mass percentage of the conductive agent in the negative electrode active material layer located in the second region and the mass percentage of the conductive agent in the negative electrode active material layer located in the first region, and / or the difference between the mass percentage of the conductive agent in the negative electrode active material layer located in the second region and the mass percentage of the conductive agent in the negative electrode active material layer located in the third region, is within the above range, the problem of accelerated capacity decay of battery cells due to excessively high kinetic performance in the first region and / or the third region located at the ends, and excessively low kinetic performance in the second region located in the middle, can be avoided or improved.

[0015] In any embodiment, the negative electrode sheet includes a negative electrode active material layer, the negative electrode active material layer includes a conductive agent, a first region includes a first conductive agent, a second region includes a second conductive agent, a third region includes a third conductive agent, the conductivity of the second conductive agent is greater than the conductivity of the first conductive agent, and / or the conductivity of the second conductive agent is greater than the conductivity of the third conductive agent. When the conductive agents used in the first, second, and third regions are different, the battery cell of this application can reduce the kinetic performance of the middle region of the negative electrode by making the conductivity of the conductive agent in the negative electrode active material layer in the second region greater than that in the first region and / or the conductivity of the conductive agent in the negative electrode active material layer in the second region greater than that in the third region. This reduces the migration and diffusion of lithium ions or sodium ions in the middle region of the negative electrode, increases the polarization of the middle region of the negative electrode, and improves the kinetic performance of the end region of the negative electrode by accelerating the migration and diffusion of lithium ions or sodium ions in the end region of the negative electrode, reducing the polarization of the end region of the negative electrode. This counteracts or weakens the problem of uneven polarization in different regions during battery cell cycling, improves the lithium or sodium deposition problem of the negative electrode and the capacity decay of the battery cell, and increases the service life of the battery cell.

[0016] In any embodiment, the negative electrode sheet includes a negative electrode active material layer, and the first region, the second region, and the third region include the same binder. The mass percentage of the binder in the negative electrode active material layer in the first region is W4. Based on the mass of the negative electrode active material layer in the second region, the mass percentage of the binder in the negative electrode active material layer in the second region is W5. Based on the mass of the negative electrode active material layer in the third region, the mass percentage of the binder in the negative electrode active material layer in the third region is W6, where W4 > W5 and / or W6 > W5. When the binder used in the first, second, and third regions is the same, the battery cell of this application can reduce the kinetic performance of the middle region of the negative electrode sheet by making the mass proportion of the binder in the negative electrode active material layer located in the first and / or third regions greater than the mass proportion of the binder in the negative electrode active material layer located in the second region. This reduces the migration and diffusion of lithium ions or sodium ions in the middle region of the negative electrode sheet, increases the polarization of the middle region of the negative electrode sheet, and improves the kinetic performance of the end region of the negative electrode sheet by accelerating the migration and diffusion of lithium ions or sodium ions in the end region of the negative electrode sheet, reducing the polarization of the end region of the negative electrode sheet. This counteracts or weakens the problem of uneven polarization in different regions during battery cell cycling, improves the lithium or sodium deposition problem of the negative electrode sheet and the capacity decay of the battery cell, and increases the service life of the battery cell.

[0017] In any embodiment, the difference between W4 and W5 is 0.5wt% to 3.1wt%, and / or the difference between W6 and W5 is 0.5wt% to 3.1wt%. By ensuring that the difference between the mass percentage of the binder in the negative electrode active material layer in the first region and the mass percentage of the binder in the negative electrode active material layer in the second region, and / or the difference between the mass percentage of the binder in the negative electrode active material layer in the third region and the mass percentage of the binder in the negative electrode active material layer in the second region, falls within the aforementioned ranges, the problem of accelerated capacity decay of battery cells due to excessively high kinetic performance in the first and / or third regions at the ends and excessively low kinetic performance in the second region in the middle, leading to lithium plating in the middle during later stages of cycling, can be avoided or mitigated.

[0018] In any embodiment, the main body further includes a fourth region and a fifth region. The main body includes a first region, a fourth region, a second region, a fifth region, and a third region distributed sequentially along the width direction. The ion diffusion coefficient of the fourth region and / or the fifth region is greater than that of the second region and less than that of the first region. The battery cell of this application divides the main body into a first region, a fourth region, a second region, a fifth region, and a third region distributed sequentially along the width direction, and makes the ion diffusion coefficient of the fourth region and / or the fifth region greater than that of the second region and less than that of the first region. The fourth region, located between the second region and the first region, and the fifth region, located between the second region and the third region, are transition regions. This reduces the polarization difference between the second region and adjacent regions, thereby making the transition from the second region to the first and third regions more stable, and thus improving the service life of the battery cell.

[0019] In any embodiment, the aspect ratio of the first region, fourth region, second region, fifth region, and third region along the width direction is 10%–15%: 5%–10%: 50%–70%: 5%–10%: 10%–15%. By ensuring that the aspect ratio of the first region, fourth region, second region, fifth region, and third region along the width direction is within the above range, it is beneficial to more accurately offset or reduce the problem of uneven polarization in different regions during battery cell cycling, based on the polarization of the negative electrode sheet during battery cell cycling, thereby improving the capacity decay of the battery cell and increasing its service life.

[0020] In any embodiment, the ratio of the lithium-ion diffusion coefficient located in the fourth and / or fifth regions to the lithium-ion diffusion coefficient located in the second region is 5 to 100. By ensuring that the ratio of the lithium-ion diffusion coefficient located in the fourth and / or fifth regions to the lithium-ion diffusion coefficient located in the second region is within the above range, the problem of accelerated capacity decay of battery cells due to excessively high kinetic performance in the fourth and / or fifth regions and excessively low kinetic performance in the second region located in the middle can be avoided or improved in the later stages of cycling, which leads to lithium plating in the middle of the battery cells.

[0021] In any embodiment, the ion diffusion coefficient located in the fourth and / or fifth regions is 10. -10 cm 2 / s~5*10 -12 cm 2 / s. By ensuring that the ion diffusion coefficients located in the fourth and / or fifth regions are within the aforementioned range, it is possible to make the ion diffusion coefficients located in the fourth and / or fifth regions greater than the ion diffusion coefficients of the second region and less than the ion diffusion coefficients of the first and / or third regions. This is beneficial for reducing the kinetic performance of the middle region of the negative electrode sheet, increasing the polarization of the middle region of the negative electrode sheet, and improving the kinetic performance of the end region of the negative electrode sheet, thereby reducing the polarization of the end region of the negative electrode sheet.

[0022] A second aspect of this application provides a battery comprising the battery cell described in the above embodiments.

[0023] A third aspect of this application provides an electrical device that includes the battery described in the above embodiments, the battery being used to provide electrical energy. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of a battery cell according to one embodiment of this application.

[0025] Figure 2 yes Figure 1 An exploded view of a battery cell according to one embodiment of this application is shown.

[0026] Figure 3 This is a schematic diagram of the negative electrode sheet according to one embodiment of this application.

[0027] Figure 4 This is a schematic diagram of the negative electrode sheet according to another embodiment of this application.

[0028] Figure 5 This is a schematic diagram of a battery module according to one embodiment of this application.

[0029] Figure 6 This is a schematic diagram of a battery pack according to one embodiment of this application.

[0030] Figure 7 yes Figure 6 An exploded view of a battery pack according to one embodiment of this application is shown.

[0031] Figure 8 This is a schematic diagram of an electrical device in which a single battery cell is used as a power source according to one embodiment of this application.

[0032] Figure 9 This is a schematic diagram of the negative electrode sheet before it is cut.

[0033] Explanation of reference numerals in the attached figures:

[0034] 1 Battery pack; 2 Upper housing; 3 Lower housing; 4 Battery module; 5 Battery cell; 51 Housing; 52 Electrode assembly; 53 Cover plate; 6 Negative electrode plate; 61 Main body; 62 Tab; 611 First end; 612 Second end; 613 Width direction; 614 First region; 615 Second region; 616 Third region; 617 Fourth region; 618 Fifth region; 619 Blank area. Detailed Implementation

[0035] The following detailed description, with appropriate reference to the accompanying drawings, discloses a battery cell, battery, and power-consuming device according to this application. However, unnecessary details may be omitted. For example, detailed descriptions of well-known facts and repetitive descriptions of essentially identical structures may be omitted. This is to avoid unnecessarily lengthy descriptions and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided to enable those skilled in the art to fully understand this application and are not intended to limit the subject matter of the claims.

[0036] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a specific parameter, it is expected that ranges of 60-110 and 80-120 are also included. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, then the following ranges are all expected: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this application, unless otherwise stated, the numerical range "ab" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have been listed in this article; "0-5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0037] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0038] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0039] Unless otherwise specified, all steps in this application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the mention that the method may also include step (c) indicates that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0040] As lithium batteries continue to develop towards higher power and higher energy density, the different operating conditions in different areas of a single battery cell result in different temperatures, currents, and expansion forces in each area. Under different operating conditions, the capacity decay in each area is different, which leads to an excessively rapid overall reversible capacity decay of the battery cell.

[0041] When using a low-rate charging and high-power discharging mode, the low charging rate has little impact on the temperature rise of the battery cell and the diffusion of lithium ions. However, during high-power discharge, heat accumulates in the middle of the battery cell because it cannot be effectively dissipated. This leads to a higher temperature, lower impedance, and lower expansion force in the middle region of the negative electrode, resulting in faster lithium ion diffusion. In contrast, the temperature, impedance, and expansion force of the end region of the negative electrode are lower than those of the center region. When recharged, lithium ions remain in the end region. During continuous charge and discharge cycles, lithium ions accumulate in the end region, causing the polarization difference between the middle and end regions of the negative electrode to increase. This results in the capacity of the middle region being consumed first. Therefore, uneven polarization within the battery cell will lead to lithium or sodium deposition problems on the negative electrode and accelerate the reversible capacity decay of the battery cell.

[0042] Based on this, this application proposes a battery cell, a battery, and an electrical device. The following provides a more detailed description of this application and its optional embodiments.

[0043] Please see Figures 1-3 , Figure 1 This is a schematic diagram of a battery cell according to one embodiment of this application. Figure 2 yes Figure 1 An exploded view of a battery cell according to one embodiment of this application is shown. Figure 3 This is a schematic diagram of the negative electrode 6 according to one embodiment of this application.

[0044] This application provides a battery cell including an electrode assembly. The electrode assembly includes a negative electrode 6, which includes a main body 61 and a tab 62. The main body 61 has a first end 611 and a second end 612 opposite to each other. The tab 62 is disposed at the first end 611. The direction in which the negative electrode 6 extends from the first end 611 to the second end 612 is the width direction 613 of the negative electrode 6. The main body 61 includes a first region 614, a second region 615, and a third region 616 sequentially distributed along the width direction 613. The ion diffusion coefficient of the first region 614 is greater than that of the second region 615, and / or the ion diffusion coefficient of the third region 616 is greater than that of the second region 615. The ion diffusion coefficient includes the lithium ion diffusion coefficient or the sodium ion diffusion coefficient.

[0045] The electrode assembly is a structure made of a positive electrode sheet, a negative electrode sheet 6 and a separator through a winding process or a stacking process.

[0046] The main body 61 of the negative electrode plate 6 is the main structure excluding the tab 62.

[0047] The tab 62 of the negative electrode plate 6 is a metal conductor that leads out the negative electrode and serves as a contact point during charging and discharging.

[0048] The first region 614 is the region near the first end 611 of the main body 61, the second region 615 is the region located in the middle of the main body 61, and the third region 616 is the region near the second end 612 of the main body 61.

[0049] In such Figure 3 In the illustrated embodiment, the first region 614, the second region 615, and the third region 616 are all rectangular.

[0050] Optionally, the first region 614 and the third region 616 are the same size.

[0051] It should be noted that the main body 61 may be divided into a first region 614, a second region 615 and a third region 616, and the negative electrode plate 6 may also include other regions besides the first region 614, the second region 615 and the third region 616. The shape and size of the first region 614, the second region 615 and the third region 616 can be determined according to the actual situation.

[0052] This application does not impose any particular limitation on the shape of the battery cell; it can be cylindrical, square, or any other arbitrary shape. For example, Figure 1 This is a square-structured battery cell used as an example.

[0053] In some implementations, refer to Figure 2The outer packaging may include a shell and a cover. The shell may include a base plate and side plates connected to the base plate, the base plate and side plates forming a receiving cavity. The shell has an opening communicating with the receiving cavity, and the cover plate can be placed over the opening to close the receiving cavity. The positive electrode, negative electrode, and separator can be formed into an electrode assembly using a winding or stacking process. The electrode assembly is encapsulated within the receiving cavity. Electrolyte is immersed in the electrode assembly. A single battery cell may contain one or more electrode assemblies, which can be selected by those skilled in the art according to specific practical needs.

[0054] The ion diffusion coefficient is the rate at which lithium ions or sodium ions diffuse within the electrode material of a lithium-ion battery or a sodium-ion battery. It is a crucial parameter for evaluating the performance of lithium-ion or sodium-ion batteries. The diffusion rate of lithium ions or sodium ions in the electrode material directly affects the battery's charge / discharge rate and overall performance. A higher diffusion coefficient indicates a faster diffusion rate of lithium ions or sodium ions, resulting in a higher charge / discharge rate and better battery performance.

[0055] When the battery cell is a lithium-ion battery, the lithium-ion diffusion coefficient of the first region 614 is greater than that of the second region 615, and / or the lithium-ion diffusion coefficient of the third region 616 is greater than that of the second region 615.

[0056] When the battery cell is a sodium-ion battery, the sodium ion diffusion coefficient of the first region 614 is greater than that of the second region 615, and / or the sodium ion diffusion coefficient of the third region 616 is greater than that of the second region 615.

[0057] The ion diffusion coefficient of different regions of the negative electrode 6 can be measured by the following method:

[0058] Intermittent current titration (GITT) was used for determination: Different regions of the negative electrode were cut into 6-point sections to form batteries. A pulsed current was applied to the battery under test, and relaxation was performed. The voltage change was recorded. Fick's law was used to derive the formula for calculating the ion diffusion coefficient, as follows:

[0059]

[0060] Where τ is the relaxation time, and n m It is the number of moles, V m It is the molar volume, S is the electrode / electrolyte contact area, and ΔE S It is the voltage change caused by the pulse, ΔE t It is the voltage change during constant current charging (discharging). The main parameters that GITT can set are: current intensity (i) and relaxation time (τ).

[0061] The battery cell of this application divides the main body 61 into a first region 614, a second region 615, and a third region 616 distributed sequentially along the width direction 613. The lithium-ion diffusion coefficient or sodium-ion diffusion coefficient of the first region 614 is greater than that of the second region 615, and / or the ion diffusion coefficient of the third region 616 is greater than that of the second region 615. The second region 615 is closer to the center of the negative electrode 6 than the first region 614 and the third region 616, thereby reducing the ion diffusion coefficient of the center of the negative electrode 6. The kinetic performance of the region, namely, slowing down the migration and diffusion of lithium ions or sodium ions in the middle region of the negative electrode 6, increasing the polarization of the middle region of the negative electrode 6, and improving the kinetic performance of the end region of the negative electrode 6, namely, accelerating the migration and diffusion of lithium ions or sodium ions in the end region of the negative electrode 6, reducing the polarization of the end region of the negative electrode 6, thereby offsetting or weakening the problem of uneven polarization in different regions during battery cell cycling, improving the lithium or sodium deposition problem of the negative electrode 6 and the capacity decay of the battery cell, and improving the service life of the battery cell.

[0062] In some embodiments, the ratio of the lithium-ion diffusion coefficient of the first region 614 to the lithium-ion diffusion coefficient of the second region 615 is 2 to 1000, and / or the ratio of the lithium-ion diffusion coefficient of the third region 616 to the lithium-ion diffusion coefficient of the second region 615 is 2 to 1000.

[0063] As an example, the ratio of the lithium-ion diffusion coefficient of the first region 614 to the lithium-ion diffusion coefficient of the second region 615 can be 5, 10, 20, 50, 100, 200, 500, 800 or 1000, and the ratio of the lithium-ion diffusion coefficient of the third region 616 to the lithium-ion diffusion coefficient of the second region 615 can be 5, 10, 20, 50, 100, 200, 500, 800 or 1000.

[0064] By ensuring that the ratio of the lithium-ion diffusion coefficient of the first region 614 to that of the second region 615 and / or the ratio of the lithium-ion diffusion coefficient of the third region 616 to that of the second region 615 are within the aforementioned range, the problem of accelerated capacity decay of battery cells due to lithium plating in the middle during the later stages of cycling can be avoided or improved. This is because the kinetic performance of the first region 614 and / or the third region 616 located at the ends is too high, while the kinetic performance of the second region 615 located in the middle is too low.

[0065] In some embodiments, the main body 61 is divided into a first region 614, a second region 615 and a third region 616 along the width direction 613, and the ratio of the lithium-ion diffusion coefficient in the first region 614 and / or the third region 616 to the lithium-ion diffusion coefficient in the second region 615 is 5 to 500.

[0066] As an example, the ratio of the lithium-ion diffusion coefficient in the first region 614 and / or the third region 616 to the lithium-ion diffusion coefficient in the second region 615 can be 5, 10, 20, 50, 100, 200 or 500.

[0067] When the main body 61 is sequentially divided into a first region 614, a second region 615, and a third region 616 along the width direction 613, by ensuring that the ratio of the lithium-ion diffusion coefficient in the first region 614 to that in the second region 615 and / or the ratio of the lithium-ion diffusion coefficient in the third region 616 to that in the second region 615 is within the aforementioned range, the problem of accelerated capacity decay of battery cells due to lithium plating in the middle during the later stages of cycling can be avoided or improved. This is because the kinetic performance of the first region 614 and / or the third region 616 at the ends is too high, while the kinetic performance of the second region 615 in the middle is too low.

[0068] In some embodiments, the lithium-ion diffusion coefficient located in the first region 614 and / or the third region 616 is 10. - 9 cm 2 / s~10 -11 cm 2 / s, the lithium-ion diffusion coefficient in the second region 615 is 10. -11 cm 2 / s~10 -12 cm 2 / s.

[0069] As an example, the lithium-ion diffusion coefficient located in the first region 614 and / or the third region 616 can be 10. - 11 cm 2 / s, 2*10 -11 cm 2 / s、5*10 -11 cm 2 / s、8*10 -11 cm 2 / s、10 -10 cm 2 / s, 2*10 -10 cm 2 / s、5*10 -10 cm 2 / s、8*10-10 cm 2 / s or 10 -9 cm 2 / s, the lithium-ion diffusion coefficient in the second region 615 can be 10. -12 cm 2 / s, 2*10 -12 cm 2 / s、5*10 -12 cm 2 / s、8*10 -12 cm 2 / s or 10 -11 cm 2 / s.

[0070] By ensuring that the lithium-ion diffusion coefficients located in the first region 614 and / or the third region 616, as well as the lithium-ion diffusion coefficients located in the second region 615, are within the aforementioned range, it is beneficial to reduce the kinetic performance of the middle region of the negative electrode 6, increase the polarization of the middle region of the negative electrode 6, and improve the kinetic performance of the end region of the negative electrode 6, thereby reducing the polarization of the end region of the negative electrode 6.

[0071] In some embodiments, the area of ​​the second region 615 accounts for 50% to 70% of the total area of ​​the main body 61.

[0072] It should be noted that you should refer to [link / reference]. Figure 3 The negative electrode 6 includes a front side and a back side. It can be understood that on the front or back side of the negative electrode 6, the area of ​​the second region 615 accounts for 50% to 70% of the total area of ​​the main body 61.

[0073] As an example, the area of ​​the second region 615 can be 50%, 55%, 60%, 65% or 70% of the total area of ​​the main body 61.

[0074] By ensuring that the area of ​​the second region 615 falls within the aforementioned range, the area sizes of the first region 614 and the third region 616 can be further divided according to the polarization of the negative electrode 6 during the battery cell cycle. This allows for more precise offsetting or mitigation of uneven polarization in different regions during battery cell cycle, improving battery cell capacity decay and extending battery cell lifespan.

[0075] In some embodiments, the ratio of the dimensions of the first region 614, the second region 615, and the third region 616 along the width direction 613 is 15%–25%: 50%–70%: 15%–25%.

[0076] As an example, the ratio of the dimensions of the first region 614, the second region 615, and the third region 616 along the width direction 613 can be 15%:70%:15%, 20%:60%:20%, 25%:50%:25%, or 15%:60%:25%.

[0077] By ensuring that the dimensions of the first region 614, the second region 615, and the third region 616 along the width direction 613 are within the aforementioned range, it is advantageous to divide the first region 614, the third region 616, and the second region 615 located at the two ends according to the polarization of the negative electrode 6 during the battery cell cycle. This allows for more precise offsetting or reduction of the problem of uneven polarization in different regions during the battery cell cycle, improving the capacity decay of the battery cell, and increasing the service life of the battery cell.

[0078] In some embodiments, the negative electrode 6 includes a negative electrode active material layer, which includes a negative electrode active material. The ion diffusion coefficient of the negative electrode active material located in the first region 614 and / or the third region 616 is greater than that of the negative electrode active material located in the second region 615.

[0079] Optionally, the negative electrode active material located in the first region 614, the negative electrode active material located in the second region 615, and the negative electrode active material located in the third region 616 are all graphite.

[0080] It should be noted that the ion diffusion coefficient of the negative electrode active material may be affected by the following factors:

[0081] 1. Material Structure and Composition: Different anode active materials have different crystal structures and chemical compositions, which directly affect the diffusion path and diffusion kinetics of lithium ions. For example, anode active materials with more open and ordered crystal structures usually have higher lithium ion diffusion coefficients.

[0082] 2. Particle size and morphology: The particle size and morphology of the negative electrode active material also affect the lithium-ion diffusion coefficient. Smaller particle size can reduce the distance that lithium ions diffuse, thereby improving the diffusion coefficient.

[0083] 3. Specific surface area: A negative electrode active material with a larger specific surface area provides more active sites, which helps to improve the diffusion rate of lithium ions.

[0084] 4. Tap density: Tap density affects the packing density of the negative electrode active material, which in turn may affect the diffusion path and diffusion coefficient of lithium ions.

[0085] 5. Electrochemical performance: This includes lithium-ion diffusion kinetics and electrochemical reduction rate. Differences in the electrochemical performance of different negative electrode active materials will lead to different lithium-ion diffusion coefficients.

[0086] 6. Material modification: By introducing high-entropy elements or modifying other materials, the crystal structure and diffusion ability of the negative electrode active material can be adjusted, thereby affecting the diffusion coefficient of lithium ions.

[0087] 7. Surface treatment: Surface treatment of the negative electrode active material, such as surface layer expansion, can improve the diffusion kinetics of lithium ions, thereby increasing the diffusion coefficient.

[0088] The battery cell of this application achieves a lithium-ion diffusion coefficient or sodium-ion diffusion coefficient in the negative electrode active material located in the first region 614 and / or the third region 616 that is greater than that in the negative electrode active material located in the second region 615. This results in a reduction in the kinetic performance of the middle region of the negative electrode 6, an increase in the polarization of the middle region of the negative electrode 6, and an improvement in the kinetic performance of the end region of the negative electrode 6, thus reducing the polarization of the end region of the negative electrode 6. This counteracts or weakens the problem of uneven polarization in different regions during battery cell cycling, improves the lithium or sodium deposition problem of the negative electrode 6 and the capacity decay of the battery cell, and increases the service life of the battery cell.

[0089] In some embodiments, the negative electrode 6 includes a negative electrode active material layer, and the first region 614, the second region 615, and the third region 616 include the same conductive agent. Based on the mass of the negative electrode active material layer in the first region 614, the mass percentage of the conductive agent in the negative electrode active material layer in the first region 614 is W1; based on the mass of the negative electrode active material layer in the second region 615, the mass percentage of the conductive agent in the negative electrode active material layer in the second region 615 is W2; based on the mass of the negative electrode active material layer in the third region 616, the mass percentage of the conductive agent in the negative electrode active material layer in the third region 616 is W3, where W1 < W2 and / or W3 < W2.

[0090] When the conductive agent used in the first region 614, the second region 615, and the third region 616 is the same, the battery cell of this application can reduce the kinetic performance of the middle region of the negative electrode 6 by making the mass ratio of the conductive agent in the negative electrode active material layer located in the second region 615 greater than the mass ratio of the conductive agent in the negative electrode active material layer located in the first region 614 and / or the third region 616. This reduces the migration and diffusion of lithium ions or sodium ions in the middle region of the negative electrode 6, increases the polarization of the middle region of the negative electrode 6, and improves the kinetic performance of the end region of the negative electrode 6. This accelerates the migration and diffusion of lithium ions or sodium ions in the end region of the negative electrode 6, reduces the polarization of the end region of the negative electrode 6, and thus offsets or weakens the problem of uneven polarization in different regions during battery cell cycling, improves the lithium or sodium plating problem of the negative electrode 6 and the capacity decay of the battery cell, and improves the service life of the battery cell.

[0091] In some implementations, the difference between W2 and W1 is 0.5wt% to 2wt%, and / or the difference between W2 and W3 is 0.5wt% to 2wt%.

[0092] As an example, the difference between W2 and W1 can be 0.5wt%, 0.8wt%, 1wt%, 1.2wt%, 1.5wt%, 1.8wt%, or 2wt%, and the difference between W2 and W3 can be 0.5wt%, 0.8wt%, 1wt%, 1.2wt%, 1.5wt%, 1.8wt%, or 2wt%.

[0093] By ensuring that the difference between the mass percentage of the conductive agent in the negative electrode active material layer located in the second region 615 and the mass percentage of the conductive agent in the negative electrode active material layer located in the first region 614, and / or the difference between the mass percentage of the conductive agent in the negative electrode active material layer located in the second region 615 and the mass percentage of the conductive agent in the negative electrode active material layer located in the third region 616, is within the aforementioned range, the problem of accelerated capacity decay of battery cells due to excessively high kinetic performance in the first region 614 and / or the third region 616 located at the ends and excessively low kinetic performance in the second region 615 located in the middle, leading to lithium plating in the middle during the later stages of cycling, can be avoided or mitigated.

[0094] In some embodiments, the negative electrode 6 includes a negative electrode active material layer, the negative electrode active material layer includes a conductive agent, a first region 614 includes a first conductive agent, a second region 615 includes a second conductive agent, a third region 616 includes a third conductive agent, the conductivity of the second conductive agent is greater than the conductivity of the first conductive agent, and / or the conductivity of the second conductive agent is greater than the conductivity of the third conductive agent.

[0095] As an example, the first and third conductive agents can be carbon black, and the second conductive agent can be carbon nanotubes; or the first and third conductive agents can be carbon black, and the second conductive agent can be graphene; or the first and third conductive agents can be carbon nanotubes, and the second conductive agent can be graphene.

[0096] When the conductive agents used in the first region 614, the second region 615, and the third region 616 are different, the battery cell of this application can reduce the kinetic performance of the central region of the negative electrode 6 by making the conductivity of the conductive agent in the negative electrode active material layer of the second region 615 greater than that in the negative electrode active material layer of the first region 614 and / or the conductivity of the conductive agent in the negative electrode active material layer of the second region 615 greater than that in the negative electrode active material layer of the third region 616. The migration and diffusion of lithium ions or sodium ions in the middle region of the negative electrode 6 is slowed down, which increases the polarization of the middle region of the negative electrode 6 and improves the dynamic performance of the end region of the negative electrode 6. That is, it accelerates the migration and diffusion of lithium ions or sodium ions in the end region of the negative electrode 6 and reduces the polarization of the end region of the negative electrode 6. This counteracts or weakens the problem of uneven polarization in different regions during the cycle of the battery cell, improves the lithium or sodium deposition problem of the negative electrode 6 and the capacity decay of the battery cell, and improves the service life of the battery cell.

[0097] In some embodiments, the negative electrode sheet 6 includes a negative electrode active material layer, and the first region 614, the second region 615 and the third region 616 include the same binder. The mass percentage of the binder in the negative electrode active material layer in the first region 614 is W4, the mass percentage of the binder in the negative electrode active material layer in the second region 615 is W5 based on the mass of the negative electrode active material layer in the second region 615, and the mass percentage of the binder in the negative electrode active material layer in the third region 616 is W6 based on the mass of the negative electrode active material layer in the third region 616, where W4 > W5 and / or W6 > W5.

[0098] When the binders used in the first region 614, the second region 615, and the third region 616 are the same, the battery cell of this application can reduce the kinetic performance of the middle region of the negative electrode 6 by making the mass ratio of the binder in the negative electrode active material layer located in the first region 614 and / or the third region 616 greater than the mass ratio of the binder in the negative electrode active material layer located in the second region 615. This reduces the migration and diffusion of lithium ions or sodium ions in the middle region of the negative electrode 6, increases the polarization of the middle region of the negative electrode 6, and improves the kinetic performance of the end region of the negative electrode 6 by accelerating the migration and diffusion of lithium ions or sodium ions in the end region of the negative electrode 6, reducing the polarization of the end region of the negative electrode 6. This counteracts or weakens the problem of uneven polarization in different regions during battery cell cycling, improves the lithium or sodium plating problem of the negative electrode 6 and the capacity decay of the battery cell, and increases the service life of the battery cell.

[0099] In some embodiments, the difference between W4 and W5 is 0.5wt% to 3.1wt%, and / or the difference between W6 and W5 is 0.5wt% to 3.1wt%.

[0100] As an example, the difference between W4 and W5 can be 0.5wt%, 0.8wt%, 1wt%, 1.2wt%, 1.5wt%, 1.8wt%, 2wt%, 2.2wt%, 2.5wt%, 2.8wt%, 3wt%, or 3.1wt%, and the difference between W6 and W5 can be 0.5wt%, 0.8wt%, 1wt%, 1.2wt%, 1.5wt%, 1.8wt%, 2wt%, 2.2wt%, 2.5wt%, 2.8wt%, 3wt%, or 3.1wt%.

[0101] By ensuring that the difference between the mass percentage of the binder in the negative electrode active material layer located in the first region 614 and the mass percentage of the binder in the negative electrode active material layer located in the second region 615, and / or the difference between the mass percentage of the binder in the negative electrode active material layer located in the third region 616 and the mass percentage of the binder in the negative electrode active material layer located in the second region 615, is within the aforementioned range, the problem of accelerated capacity decay of battery cells due to excessively high kinetic performance in the first region 614 and / or the third region 616 located at the ends and excessively low kinetic performance in the second region 615 located in the middle, leading to lithium plating in the middle during the later stages of cycling, can be avoided or mitigated.

[0102] Please see Figure 4 , Figure 4This is a schematic diagram of the negative electrode sheet 6 according to another embodiment of this application. The main body 61 also includes a fourth region 617 and a fifth region 618. The main body 61 includes a first region 614, a fourth region 617, a second region 615, a fifth region 618 and a third region 616 distributed sequentially along the width direction 613. The ion diffusion coefficient of the fourth region 617 and / or the fifth region 618 is greater than the ion diffusion coefficient of the second region 615 and less than the ion diffusion coefficient of the first region 614.

[0103] The fourth region 617 is a transition region between the first region 614 and the second region 615, and the fifth region 618 is a transition region between the third region 616 and the second region 615.

[0104] In such Figure 4 In the embodiment shown, the first region 614, the fourth region 617, the second region 615, the fifth region 618, and the third region 616 are all rectangular.

[0105] Optionally, the fourth region 617 and the fifth region 618 are the same size.

[0106] The battery cell of this application divides the main body 61 into a first region 614, a fourth region 617, a second region 615, a fifth region 618, and a third region 616 distributed sequentially along the width direction 613. The ion diffusion coefficient of the fourth region 617 and / or the fifth region 618 is greater than that of the second region 615 and less than that of the first region 614. The fourth region 617, which is located between the second region 615 and the first region 614, and the fifth region 618, which is located between the second region 615 and the third region 616, are transition regions. The polarization difference between the second region 615 and the adjacent regions is reduced, thereby making the transition from the second region 615 to the first region 614 and the third region 616 more stable, and thus improving the service life of the battery cell.

[0107] In some embodiments, the dimensions of the first region 614, the fourth region 617, the second region 615, the fifth region 618, and the third region 616 along the width direction 613 are in the ratio of 10% to 15%: 5% to 10%: 50% to 70%: 5% to 10%: 10% to 15%.

[0108] As an example, the dimensions of the first region 614, the fourth region 617, the second region 615, the fifth region 618, and the third region 616 along the width direction 613 are 10%:5%:70%:5%:10%, 15%:5%:60%:5%:15%, 10%:10%:60%:10%:10%, 15%:10%:50%:10%:15%, 10%:5%:65%:5%:15%, or 10%:5%:60%:10%:15%.

[0109] By ensuring that the dimensions of the first region 614, the fourth region 617, the second region 615, the fifth region 618, and the third region 616 along the width direction 613 are within the aforementioned range, it is beneficial to more accurately offset or reduce the problem of uneven polarization in different regions during the cycle of the battery cell, based on the polarization of the negative electrode 6 during the cycle of the battery cell, thereby improving the capacity decay of the battery cell and increasing its service life.

[0110] In some embodiments, the ratio of the lithium-ion diffusion coefficient located in the fourth region 617 and / or the fifth region 618 to the lithium-ion diffusion coefficient located in the second region 615 is 5 to 100.

[0111] As an example, the ratio of the lithium-ion diffusion coefficient in the fourth region 617 and / or the fifth region 618 to the lithium-ion diffusion coefficient in the second region 615 can be 5, 10, 20, 50, 80 or 100.

[0112] By ensuring that the ratio of the lithium-ion diffusion coefficient in the fourth region 617 and / or the fifth region 618 to the lithium-ion diffusion coefficient in the second region 615 is within the aforementioned range, the problem of accelerated capacity decay of battery cells due to lithium plating in the middle during the later stages of cycling can be avoided or improved, as the kinetic performance of the fourth region 617 and / or the fifth region 618 is too high while the kinetic performance of the second region 615 in the middle is too low.

[0113] In some embodiments, the ion diffusion coefficient located in the fourth region 617 and / or the fifth region 618 is 10. - 10 cm 2 / s~5*10 -12 cm 2 / s.

[0114] As an example, the ion diffusion coefficient located in the fourth region 617 and / or the fifth region 618 can be 5*10. - 12 cm 2 / s、8*10 -12 cm 2 / s、10 -11 cm2 / s, 2*10 -11 cm 2 / s、5*10 -11 cm 2 / s、8*10 -11 cm 2 / s or 10 -10 cm 2 / s.

[0115] By ensuring that the ion diffusion coefficients of the fourth region 617 and / or the fifth region 618 are within the aforementioned range, it is possible to make the ion diffusion coefficients of the fourth region 617 and / or the fifth region 618 greater than the ion diffusion coefficient of the second region 615 and less than the ion diffusion coefficients of the first region 614 and / or the third region 616. This is beneficial for reducing the kinetic performance of the middle region of the negative electrode 6, increasing the polarization of the middle region of the negative electrode 6, and improving the kinetic performance of the end region of the negative electrode 6, thereby reducing the polarization of the end region of the negative electrode 6.

[0116] In addition, the following description, with appropriate reference to the accompanying drawings, will illustrate a battery cell, battery, and power-consuming device of this application.

[0117] [Battery cell]

[0118] This application does not impose any particular restrictions on the type of battery cell; for example, the battery cell can be a lithium-ion battery, etc.

[0119] Typically, a battery cell includes a positive electrode, a negative electrode, an electrolyte, and a separator. During charging and discharging, active ions move back and forth between the positive and negative electrodes, inserting and releasing. The electrolyte acts as a conductor of ions between the positive and negative electrodes. The separator, positioned between the positive and negative electrodes, primarily prevents short circuits while allowing ions to pass through.

[0120] This application does not impose any particular limitation on the type of electrolyte, which can be selected according to actual needs. For example, the electrolyte can be selected from at least one of solid electrolytes and liquid electrolytes (i.e., electrolyte solutions). This includes battery cells using electrolyte solutions and some battery cells using solid electrolytes.

[0121] [Positive electrode plate]

[0122] The positive electrode includes a positive current collector and a positive electrode film layer disposed on at least one surface of the positive current collector, the positive electrode film layer including a positive electrode active material.

[0123] As an example, the positive current collector has two surfaces opposite each other in its own thickness direction, and the positive electrode film layer is disposed on either or both of the two opposite surfaces of the positive current collector.

[0124] In some embodiments, the positive current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymer substrate and a metal layer formed on at least one surface of the polymer substrate. The composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0125] In some embodiments, when the battery cell is a lithium-ion battery, the positive electrode active material may be a positive electrode active material known in the art for lithium-ion batteries. As an example, the positive electrode active material may include at least one of the following materials: lithium phosphates with an olivine structure, lithium transition metal oxides, and their respective modified compounds. However, this application is not limited to these materials, and other conventional materials that can be used as battery positive electrode active materials may also be used. These positive electrode active materials may be used alone or in combination of two or more. Examples of lithium transition metal oxides include, but are not limited to, lithium cobalt oxides (such as LiCoO2), lithium nickel oxides (such as LiNiO2), lithium manganese oxides (such as LiMnO2, LiMn2O4), lithium nickel cobalt oxides, lithium manganese cobalt oxides, lithium nickel manganese oxides, and lithium nickel cobalt manganese oxides (such as LiNi). 1 / 3 Co 1 / 3Mn 1 / 3 O2 (also known as NCM) 333 LiNi 0.5 Co 0.2 Mn 0.3 O2 (also known as NCM) 523 LiNi 0.5 Co 0.25 Mn 0.25 O2 (also known as NCM) 211 LiNi 0.6 Co 0.2 Mn 0.2 O2 (also known as NCM) 622 LiNi 0.8 Co 0.1 Mn 0.1 O2 (also known as NCM) 811 ), lithium nickel cobalt aluminum oxide (such as LiNi) 0.8 Co 0.15 Al 0.05at least one of O2) and its modified compounds. Examples of the lithium phosphate with olivine structure may include, but are not limited to, lithium iron phosphate (such as LiFePO4 (which can also be abbreviated as LFP)), a composite material of lithium iron phosphate and carbon, lithium manganese phosphate (such as LiMnPO4), a composite material of lithium manganese phosphate and carbon, lithium manganese iron phosphate, and a composite material of lithium manganese iron phosphate and carbon.

[0126] In some embodiments, in order to further improve the energy density of the battery cell, the positive electrode active material for the lithium ion battery may include a lithium transition metal oxide having the general formula Li a Ni b Co c M d O e A f and one or more of its modified compounds. 0.8 ≤ a ≤ 1.2, 0.5 ≤ b < 1, 0 < c < 1, 0 < d < 1, 1 ≤ e ≤ 2, 0 ≤ f ≤ 1, M is selected from one or more of Mn, Al, Zr, Zn, Cu, Cr, Mg, Fe, V, Ti, and B, and A is selected from one or more of N, F, S, and Cl.

[0127] In some embodiments, by way of example, the positive electrode active material for the lithium ion battery may include LiCoO2, LiNiO2, LiMnO2, LiMn2O4, LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (NCM333), LiNi 0.5 Co 0.2 Mn 0.3 O2 (NCM523), LiNi 0.6 Co 0.2 Mn 0.2 O2 (NCM622), LiNi 0.8 Co 0.1 Mn 0.1 O2 (NCM811), LiNi 0.85 Co 0.15 Al 0.05 O2, LiFePO4, and LiMnPO4.

[0128] In the present application, the modified compounds of the above positive electrode active materials may be doping modification and / or surface coating modification of the positive electrode active materials.

[0129] As an optional technical solution of the present application, the polyanionic compound may be Li 1+x Mn 1-y A y P 1-z R zO4; where x is any value in the range of -0.100 to 0.100, y is any value in the range of 0.001 to 0.500, z is any value in the range of 0.001 to 0.100, A includes one or more elements selected from Zn, Al, Na, K, Mg, Mo, W, Ti, V, Zr, Fe, Ni, Co, Ga, Sn, Sb, Nb and Ge, and R includes one or more elements selected from B, S, Si and N;

[0130] As an optional technical approach in this application, the polyanionic compound can be Li a A e Mn 1-f B f P 1-g C g O 4-n D n Wherein, A includes one or more elements selected from Zn, Al, Na, K, Mg, Nb, Mo, and W; B includes one or more elements selected from Ti, V, Zr, Fe, Ni, Mg, Co, Ga, Sn, Sb, Nb, and Ge; C includes one or more elements selected from B, S, Si, and N; D includes one or more elements selected from S, F, Cl, and Br; a is selected from the range of 0.9 to 1.1, e is selected from the range of 0.001 to 0.1, f is selected from the range of 0.001 to 0.5, g is selected from the range of 0.001 to 0.1, n is selected from the range of 0.001 to 0.1, and the second positive electrode active material is electrically neutral.

[0131] During the charging and discharging process of a battery, Li undergoes insertion / extraction and consumption, resulting in varying molar Li content at different discharge states. In the examples of cathode materials in this application, the molar Li content refers to the initial state of the material, i.e., the state before feeding. When the cathode material is applied to the battery system, the molar Li content changes after charge-discharge cycles.

[0132] In the examples of cathode materials in this application, the molar content of O is only a theoretical value. Oxygen release from the crystal lattice will cause changes in the molar content of oxygen, and the actual molar content of O will fluctuate.

[0133] When the battery cell is a sodium-ion battery, the positive electrode active material can be any positive electrode active material known in the art for use in sodium-ion batteries. As an example, the positive electrode active material may include at least one of the following materials: polyanionic compounds, sodium transition metal oxides, Prussian blue compounds, and their respective modified compounds. However, this application is not limited to these materials, and other conventional materials that can be used as positive electrode active materials for batteries may also be used. These positive electrode active materials may be used alone or in combination of two or more.

[0134] As an optional technical solution of the present application, the polyanionic compound can be Na 4+x R 3-y P 4-m O 15 / C; wherein, 0 < x < 0.5, 0 < y ≤ 0.5, 0 < m ≤ 0.2, and R includes at least one of Mg, Al, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Zr, Cr, Nb, Mo, In, Ga, Sn, Hf, Ta, W, and Pb.

[0135] As an optional technical solution of the present application, the polyanionic compound can be Na x-a A a V y-b M b (PO4) 2-2c (DO4) 2c F z-d Q d , where the A element represents an alkali metal element that dopes and replaces the Na element, the M element represents a metal element that replaces the V element, the D element represents a doping element that replaces the P element, the Q element represents a doping element that replaces the F element, the D element includes at least one of Si and S, the Q element includes at least one of Cl and O; 3.5 ≤ x ≤ 4.5, 0 ≤ a ≤ 0.15x, 0.8 ≤ y ≤ 1.1, 0 ≤ b ≤ 0.3y, 0 ≤ c ≤ 0.15, 0.8 ≤ z ≤ 1.1, 0 ≤ d ≤ 0.2z. Optionally, the A element includes at least one of K and Li; the M element includes at least one of Fe, Cr, Al, Sc, Ga, In, Ti, Zr, Mn, Zn, Ni, Cu, and Co.

[0136] As an optional technical solution of the present application, the polyanionic compound can be a type of compound having sodium ions, transition metal ions, and a tetrahedral (YO4) n- anionic unit. The transition metal can be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce; Y can be at least one of P, S, and Si; n represents the valence state of (YO4) n- .

[0137] The polyanionic compound can also be a type of compound having sodium ions, transition metal ions, a tetrahedral (YO4) n- anionic unit, and a halogen anion. The transition metal can be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce; Y can be at least one of P, S, and Si; n represents the valence state of (YO4) n- ; the halogen can be at least one of F, Cl, and Br.

[0138] Polyanionic compounds can also be sodium-containing tetrahedral (YO4) compounds. n- Anionic unit, polyhedral unit (ZO) y ) m+ And a class of compounds with optional halide anions. Y can be at least one of P, S, and Si, n represents the valence state of V; Z represents a transition metal, which can be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce, m represents (ZO) y ) m+ The valence state; the halogen can be at least one of F, Cl and Br.

[0139] Polyanionic compounds include, for example, NaFePO4, Na3V2(PO4)3, NaM'PO4F (where M' is one or more of V, Fe, Mn, and Ni) and Na3(VO y )2(PO4)2F 3-2y At least one of (0≤y≤1).

[0140] As an optional technical solution in this application, in the sodium transition metal oxide, the transition metal can be at least one selected from Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce. For example, the sodium transition metal oxide is Na. x MO2, where M is one or more of Ti, V, Mn, Co, Ni, Fe, Cr, and Cu, 0 <x≤1。

[0141] As an optional technical solution in this application, Prussian blue compounds may be those containing sodium ions, transition metal ions, and cyanide ions (CN). - A class of compounds. The transition metal can be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce. Prussian blue compounds are, for example, Na. a Me b Me' c (CN)6, wherein Me and Me' are each independently at least one of Ni, Cu, Fe, Mn, Co, and Zn, 0 <a≤2,0<b<1,0<c<1。

[0142] In some embodiments, the positive electrode film layer may optionally include a binder. As an example, the binder may include at least one selected from polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resin.

[0143] In some embodiments, the positive electrode film may optionally include a conductive agent. As an example, the conductive agent may include at least one selected from superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0144] In some embodiments, the positive electrode sheet can be prepared by dispersing the above-mentioned components for preparing the positive electrode sheet, such as positive active material, conductive agent, binder and any other components, in a solvent (e.g., N-methylpyrrolidone) to form a positive electrode slurry; coating the positive electrode slurry onto the positive electrode current collector, and then obtaining the positive electrode sheet after drying, cold pressing and other processes.

[0145] [Negative electrode plate]

[0146] In some embodiments, the negative electrode sheet includes a negative current collector and a negative electrode film layer disposed on at least one surface of the negative current collector.

[0147] As an example, the negative electrode current collector has two surfaces opposite each other in its own thickness direction, and the negative electrode film layer is disposed on either or both of the two opposite surfaces of the negative electrode current collector.

[0148] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, copper foil may be used as the metal foil. The composite current collector may include a polymer substrate and a metal layer formed on at least one surface of the polymer substrate. The composite current collector may be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0149] In some embodiments, the negative electrode film layer includes a negative electrode active material. The negative electrode active material may be any negative electrode active material known in the art for use in batteries. As an example, the negative electrode active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate, etc. The silicon-based material may be selected from at least one of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. The tin-based material may be selected from at least one of elemental tin, tin oxide compounds, and tin alloys. However, this application is not limited to these materials, and other conventional materials that can be used as negative electrode active materials for batteries may also be used. These negative electrode active materials may be used alone or in combination of two or more.

[0150] In some embodiments, the negative electrode film layer may optionally include a binder. The binder may be selected from at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0151] In some embodiments, the negative electrode film may optionally include a conductive agent. The conductive agent may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0152] In some embodiments, the negative electrode film may optionally include other additives, such as thickeners (e.g., sodium carboxymethyl cellulose (CMC-Na)).

[0153] In some embodiments, the negative electrode sheet can be prepared by dispersing the components used to prepare the negative electrode sheet, such as the negative electrode active material, conductive agent, binder and any other components, in a solvent (e.g., deionized water) to form a negative electrode slurry; coating the negative electrode slurry onto the negative electrode current collector, and then obtaining the negative electrode sheet after drying, cold pressing and other processes.

[0154] In other embodiments, the current collector of the negative electrode sheet typically includes a current collector body and a base coating. The base coating can be disposed on at least one side of the current collector body. The base coating basically does not contain negative electrode active material, and may include a small amount of carbon material. However, the carbon material forms a thin coating and cannot function as a negative electrode active material. In this embodiment, the negative electrode sheet can be an electrode sheet without a negative electrode active material layer. For a negative electrode sheet without a negative electrode active material layer, when the current collector of the negative electrode sheet does not contain a base coating, the film layer can be disposed on the surface of at least one side of the current collector; when the current collector of the negative electrode sheet includes a base coating, the film layer can be disposed on the surface of the base coating away from the current collector.

[0155] In some embodiments, the film layer may further include a binder for fixing the additive to the negative electrode sheet. The type of binder is not particularly limited, and those skilled in the art can choose flexibly according to actual needs.

[0156] [Electrolytes]

[0157] The electrolyte acts as a conductor of ions between the positive and negative electrodes. This application does not impose specific restrictions on the type of electrolyte; it can be selected according to requirements. For example, the electrolyte can be liquid, gel, or entirely solid.

[0158] In some embodiments, the electrolyte is an electrolyte solution. The electrolyte solution includes an electrolyte salt and a solvent.

[0159] In some embodiments, when the battery cell is a lithium-ion battery, the electrolyte salt may be selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalate borate, lithium dioxalate borate, lithium difluorodiooxalate phosphate, and lithium tetrafluorooxalate phosphate. When the battery cell is a sodium-ion battery, the electrolyte salt may be selected from at least one of sodium hexafluorophosphate, sodium tetrafluoroborate, sodium perchlorate, sodium hexafluoroarsenate, sodium bis(fluorosulfonyl)imide, and sodium difluorooxalate borate.

[0160] In some embodiments, the solvent may be selected from at least one of ethylene carbonate, propylene carbonate, methyl ethyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butyl carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, sulfolane, dimethyl sulfone, methyl ethyl sulfone, and diethyl sulfone.

[0161] In some embodiments, the electrolyte may optionally include additives. For example, additives may include negative electrode film-forming additives, positive electrode film-forming additives, and may also include additives that can improve certain battery performance, such as additives that improve battery overcharge performance, additives that improve battery high-temperature or low-temperature performance, etc.

[0162] [Isolation membrane]

[0163] In some embodiments, the battery cell also includes a separator. This application does not impose any particular limitation on the type of separator; any known porous separator with good chemical and mechanical stability can be selected.

[0164] In some embodiments, the material of the separator can be selected from at least one of glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator can be a single-layer film or a multi-layer composite film, without particular limitation. When the separator is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation.

[0165] In some embodiments, the battery cell may include an outer packaging. This outer packaging can be used to encapsulate the electrode assembly and electrolyte described above.

[0166] In some embodiments, the outer packaging of the battery cell can be a rigid shell, such as a hard plastic shell, an aluminum shell, or a steel shell. The outer packaging of the battery cell can also be a flexible package, such as a pouch. The material of the flexible package can be plastic; examples of plastics include polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0167] This application does not impose any particular limitation on the shape of the battery cell; it can be cylindrical, square, or any other arbitrary shape. For example, Figure 1 The example shown is a square-structured battery cell 5.

[0168] In some implementations, refer to Figure 2 The outer packaging may include a housing 51 and a cover plate 53. The housing 51 may include a base plate and side plates connected to the base plate, the base plate and side plates forming a receiving cavity. The housing 51 has an opening communicating with the receiving cavity, and the cover plate 53 can be placed over the opening to close the receiving cavity. The positive electrode sheet, negative electrode sheet, and separator can be formed into an electrode assembly 52 by a winding process or a stacking process. The electrode assembly 52 is encapsulated within the receiving cavity. Electrolyte is immersed in the electrode assembly 52. ​​The number of electrode assemblies 52 contained in a single battery cell 5 can be one or more, which can be selected by those skilled in the art according to specific practical needs.

[0169] In some implementations, individual battery cells can be assembled into a battery module. The number of individual battery cells contained in a battery module can be one or more, and the specific number can be selected by those skilled in the art based on the application and capacity of the battery module.

[0170] Figure 5 This is battery module 4, used as an example. (See reference...) Figure 5 In battery module 4, multiple battery cells 5 can be arranged sequentially along the length of battery module 4. Of course, they can also be arranged in any other manner. Furthermore, these multiple battery cells 5 can be fixed in place using fasteners.

[0171] Optionally, the battery module 4 may also include a housing with a receiving space in which multiple battery cells 5 are received.

[0172] In some embodiments, the battery modules described above can also be assembled into a battery pack, and the number of battery modules contained in the battery pack can be one or more, the specific number of which can be selected by those skilled in the art according to the application and capacity of the battery pack.

[0173] Figure 6 and Figure 7 This is battery pack 1 as an example. (See reference...) Figure 6 and Figure 7 The battery pack 1 may include a battery box and multiple battery modules 4 disposed within the battery box. The battery box includes an upper body 2 and a lower body 3, with the upper body 2 covering the lower body 3 to form a closed space for accommodating the battery modules 4. The multiple battery modules 4 can be arranged in any manner within the battery box.

[0174] In addition, this application also provides an electrical device, which includes at least one of the battery cell, battery module, or battery pack provided in this application. The battery cell, battery module, or battery pack can be used as a power source for the electrical device, or as an energy storage unit for the electrical device. The electrical device may include, but is not limited to, mobile devices (e.g., mobile phones, laptops, etc.), electric vehicles (e.g., pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc.

[0175] As the electrical device, a single battery cell, a battery module, or a battery pack can be selected according to its usage requirements.

[0176] Figure 8 This is an example of an electrical device. The device could be a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the high power and high energy density requirements of individual battery cells, a battery pack or battery module can be used.

[0177] Another example device could be a mobile phone, tablet, or laptop. These devices typically require a slim and lightweight design and can use a single battery cell as their power source.

[0178] Example

[0179] The following describes embodiments of this application. The embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all conventional products that can be obtained commercially.

[0180] Examples 1-8 of this application provide a battery cell and a method for preparing the same, which includes the following steps:

[0181] S1. Preparation of positive electrode sheet

[0182] Lithium iron phosphate (LiFePO4), conductive carbon black (sp), and polyvinylidene fluoride (PVDF) were mixed in a weight ratio of 97:1:2 and dissolved in N-methylpyrrolidone (NMP) to prepare a positive electrode slurry. The positive electrode slurry was then uniformly coated onto a 15 μm aluminum foil with a coating weight of 0.068 CW / 1540.25 mm. 2 After being fully dried, the positive electrode sheet is obtained by cold pressing, die cutting, and slitting.

[0183] S2, Preparation of negative electrode sheet

[0184] Preparation of slurries: Two types of graphite with different kinetics were prepared. High-kinetic-performance graphite, conductive carbon black (SP), and styrene-butadiene rubber (SBR) were mixed in a weight ratio of 97.5:1:1.5 and dissolved in deionized water to prepare the first negative electrode slurry. Low-kinetic-performance graphite, conductive carbon black (SP), and SBR were mixed in a weight ratio of 97.5:1:1.5 and dissolved in deionized water to prepare the second negative electrode slurry. The lithium-ion diffusion coefficient of the high-kinetic-performance graphite was greater than that of the low-kinetic-performance graphite. The first negative electrode slurry was then coated onto specific areas of the current collector copper foil to form the first and third regions of the negative electrode sheet. The second negative electrode slurry was coated onto specific areas of the current collector copper foil to form the second region of the negative electrode sheet. The coating weight of both the first and second negative electrode slurries was 0.162 CW / 1540.25 mm. 2 After drying, cold pressing, and slitting, negative electrode sheets are obtained, such as... Figure 9 As shown, blank area 619 is the area used to form the electrode tab.

[0185] S3. Preparation of the isolation membrane

[0186] Using a conventional PE base film with a thickness of 5μm, ceramic fiber, styrene-butadiene rubber, polyvinylidene fluoride and water are mixed evenly in a mass ratio of 4:0.9:0.1:5 to obtain a ceramic fiber slurry. The slurry is then uniformly coated onto the surface of the base film using a gravure coating method to form a ceramic fiber layer, and dried at 45℃ to obtain a separator membrane.

[0187] S4. Preparation of electrolyte

[0188] In an argon atmosphere glove box (H2O < 0.1 ppm, O2 < 0.1 ppm), ethylene carbonate (EC) and ethyl methyl carbonate (EMC) were mixed uniformly at a volume ratio of 3:7. 1 mol / L LiPF6 lithium salt was added and dissolved in the organic solvent and stirred until homogeneous to obtain the electrolyte.

[0189] S5, Assembly

[0190] The positive electrode, separator, and negative electrode are stacked in sequence, with the separator positioned between the positive and negative electrodes for isolation. They are then wound to obtain a bare cell. Tabs are welded onto the bare cell, which is then placed in an aluminum casing and baked at 80°C to remove moisture. Electrolyte is then injected and the casing is sealed, resulting in a non-charged battery. This non-charged battery then undergoes a series of processes including settling, formation, shaping, and capacity testing to obtain a single battery cell. Figures 1-3 As shown.

[0191] Examples 9-12 of this application provide a battery cell and a method for preparing the same, which includes the following steps:

[0192] S1. Preparation of positive electrode sheet

[0193] Lithium iron phosphate (LiFePO4), conductive carbon black (sp), and polyvinylidene fluoride (PVDF) were mixed in a weight ratio of 97:1:2 and dissolved in N-methylpyrrolidone (NMP) to prepare a positive electrode slurry. The positive electrode slurry was then uniformly coated onto a 15 μm aluminum foil with a coating weight of 0.068 CW / 1540.25 mm. 2 After being fully dried, the positive electrode sheet is obtained by cold pressing, die cutting, and slitting.

[0194] S2. Preparation of negative electrode sheet

[0195] Preparation of slurries: Three types of graphite with different kinetics were prepared. High-kinetic graphite, conductive carbon black (SP), and styrene-butadiene rubber (SBR) were mixed in a weight ratio of 97.5:1:1.5 and dissolved in deionized water to prepare the first negative electrode slurry. Low-kinetic graphite, conductive carbon black (SP), and SBR were mixed in a weight ratio of 97.5:1:1.5 and dissolved in deionized water to prepare the second negative electrode slurry. Medium-kinetic graphite, conductive carbon black (SP), and SBR were mixed in a weight ratio of 97.5:1:1.5 and dissolved in deionized water to prepare the third negative electrode slurry. The high-kinetic graphite… The lithium-ion diffusion coefficient of mechanically active graphite is greater than that of medium-kinetic graphite, which in turn is greater than that of low-kinetic graphite. Then, a first negative electrode slurry is coated onto a specific area of ​​the current collector copper foil to form the first and third regions of the negative electrode sheet; a second negative electrode slurry is coated onto a specific area of ​​the current collector copper foil to form the second region of the negative electrode sheet; and a third negative electrode slurry is coated onto a specific area of ​​the current collector copper foil to form the fourth and fifth regions of the negative electrode sheet. The coating weight of the first, second, and third negative electrode slurries is 0.162 CW / 1540.25 mm. 2 The negative electrode sheet is obtained by drying, cold pressing, and slitting.

[0196] S3. Preparation of the isolation membrane

[0197] Using a conventional PE base film with a thickness of 5μm, ceramic fiber, styrene-butadiene rubber, polyvinylidene fluoride and water are mixed evenly in a mass ratio of 4:0.9:0.1:5 to obtain a ceramic fiber slurry. The slurry is then uniformly coated onto the surface of the base film using a gravure coating method to form a ceramic fiber layer, and dried at 45℃ to obtain a separator membrane.

[0198] S4. Preparation of electrolyte

[0199] In an argon atmosphere glove box (H2O < 0.1 ppm, O2 < 0.1 ppm), ethylene carbonate (EC) and ethyl methyl carbonate (EMC) were mixed uniformly at a volume ratio of 3:7. 1 mol / L LiPF6 lithium salt was added and dissolved in the organic solvent and stirred until homogeneous to obtain the electrolyte.

[0200] S5, Assembly

[0201] The positive electrode, separator, and negative electrode are stacked in sequence, with the separator positioned between the positive and negative electrodes for isolation. They are then wound to obtain a bare cell. Tabs are welded onto the bare cell, which is then placed in an aluminum casing and baked at 80°C to remove moisture. Electrolyte is then injected and the casing is sealed, resulting in a non-charged battery. This non-charged battery then undergoes a series of processes including settling, formation, shaping, and capacity testing to obtain a single battery cell. Figures 1-2 As shown in Figure 4.

[0202] Comparative Examples 1-3 of this application provide a battery cell and a method for preparing the same, which includes the following steps:

[0203] S1. Preparation of positive electrode sheet

[0204] Lithium iron phosphate (LiFePO4), conductive carbon black (sp), and polyvinylidene fluoride (PVDF) were mixed in a weight ratio of 97:1:2 and dissolved in N-methylpyrrolidone (NMP) to prepare a positive electrode slurry. The positive electrode slurry was then uniformly coated onto a 15 μm aluminum foil with a coating weight of 0.068 CW / 1540.25 mm. 2 After being fully dried, the positive electrode sheet is obtained by cold pressing, die cutting, and slitting.

[0205] S2, Preparation of negative electrode sheet

[0206] Preparation of the slurry: Graphite was prepared, and graphite, conductive carbon black (SP), and styrene-butadiene rubber were mixed in a weight ratio of 97.5:1:1.5 and dissolved in deionized water to prepare the negative electrode slurry. Then, the negative electrode slurry was coated onto the surface of the copper foil current collector to form the negative electrode sheet. The coating weight of the negative electrode slurry was 0.162 CW / 1540.25 mm. 2 The negative electrode sheet is obtained by drying, cold pressing, and slitting.

[0207] S3. Preparation of the isolation membrane

[0208] Using a conventional PE base film with a thickness of 5μm, ceramic fiber, styrene-butadiene rubber, polyvinylidene fluoride and water are mixed evenly in a mass ratio of 4:0.9:0.1:5 to obtain a ceramic fiber slurry. The slurry is then uniformly coated onto the surface of the base film using a gravure coating method to form a ceramic fiber layer, and dried at 45℃ to obtain a separator membrane.

[0209] S4. Preparation of electrolyte

[0210] In an argon atmosphere glove box (H2O < 0.1 ppm, O2 < 0.1 ppm), ethylene carbonate (EC) and ethyl methyl carbonate (EMC) were mixed uniformly at a volume ratio of 3:7. 1 mol / L LiPF6 lithium salt was added and dissolved in the organic solvent and stirred until homogeneous to obtain the electrolyte.

[0211] S5, Assembly

[0212] The positive electrode, separator, and negative electrode are stacked in sequence, with the separator positioned between the positive and negative electrodes for isolation. They are then wound to obtain a bare cell. Tabs are welded onto the bare cell, which is then placed in an aluminum casing and baked at 80°C to remove moisture. Electrolyte is then injected and the casing is sealed, resulting in a non-charged battery. This non-charged battery then undergoes a series of processes including settling, formation, shaping, and capacity testing to obtain a single battery cell. Figures 1-2 As shown.

[0213] The types of graphite used in different regions of the battery cells in Examples 1-12 and Comparative Examples 1-3 are shown in Table 1.

[0214] Table 1 shows the types of graphite used in different regions of the battery cells in Examples 1-12 and Comparative Examples 1-3.

[0215]

[0216] Among them, the lithium-ion diffusion coefficient of graphite A is 1.8*10. -11 The lithium-ion diffusion coefficient of graphite B is 6.6*10. -12 The lithium-ion diffusion coefficient of graphite C is 1*10. -9 The lithium-ion diffusion coefficient of graphite D is 1*10. -11 The lithium-ion diffusion coefficient of graphite E is 1*10. -12 The lithium-ion diffusion coefficient of graphite F is 1.7*10. -12 The lithium-ion diffusion coefficient of graphite G is 1*10. -10 The lithium-ion diffusion coefficient of graphite H is 1.1*10. -11 .

[0217] The lithium-ion diffusion coefficient of graphite was determined by intermittent current titration (GITT): different graphites were made into negative electrode sheets, and then the negative electrode sheets were used to make batteries (the preparation method of the batteries was the same as that of comparative examples 1-3). The voltage change of the battery under test was recorded by applying a pulse current and relaxing the battery. The formula for calculating the lithium-ion diffusion coefficient was derived from Fick's law as follows:

[0218]

[0219] Where τ is the relaxation time, and n m It is the number of moles, Vm It is the molar volume, S is the electrode / electrolyte contact area, and ΔE S It is the voltage change caused by the pulse, ΔE t It is the voltage change during constant current charging (discharging). The main parameters that GITT can set are: current intensity (i) and relaxation time (τ).

[0220] The relevant parameters of the battery cells in Examples 1-12 and Comparative Examples 1-3 are shown in Table 2.

[0221] Table 2. Relevant parameters of the battery cells in Examples 1-12 and Comparative Examples 1-3.

[0222]

[0223]

[0224] The lithium-ion diffusion coefficient of different regions of the negative electrode sheet was determined by intermittent current titration (GITT): the negative electrode sheets of different regions were cut into batteries, and the voltage changes of the battery under test were recorded by applying a pulse current and relaxation. The formula for calculating the lithium-ion diffusion coefficient was derived from Fick's law as follows:

[0225]

[0226] Where τ is the relaxation time, and n m It is the number of moles, V m It is the molar volume, S is the electrode / electrolyte contact area, and ΔE S It is the voltage change caused by the pulse, ΔE t It is the voltage change during constant current charging (discharging). The main parameters that GITT can set are: current intensity (i) and relaxation time (τ).

[0227] In addition, the cycle performance of the battery cells of Examples 1-12 and Comparative Examples 1-3 was measured, and the results are shown in Table 3.

[0228] The testing method is as follows:

[0229] S1. Allow the individual battery cells to stand still for 2 hours;

[0230] S2 and 1C are discharged to 2.5V;

[0231] S3, rest for 5 minutes;

[0232] S4, 1C charging to 3.65V;

[0233] S5, stand still for 60 minutes;

[0234] S6, 358W constant power discharge to 2.5V;

[0235] S7, remain still for 2 hours;

[0236] S8. Repeat steps S4 to S7 until the SOC of a single battery cell reaches 80%, and record the number of cycles.

[0237] Table 3 shows the cycle performance of the battery cells in Examples 1-12 and Comparative Examples 1-3.

[0238] project 80% SOC cycle count (cls) Example 1 1683 Example 2 2126 Example 3 1557 Example 4 1466 Example 5 2264 Example 6 1585 Example 7 1446 Example 8 1934 Example 9 2347 Example 10 2262 Example 11 2388 Example 12 2160 Comparative Example 1 1316 Comparative Example 2 989 Comparative Example 3 1229

[0239] As can be seen from Examples 1 to 8, the main body of the negative electrode sheet in Examples 1 to 8 is divided into a first region, a second region and a third region. Along the width direction, the negative electrode sheet is in the first region, the second region and the third region in sequence, and the number of cycles at 80% SOC of the battery cell is 1446 to 2264.

[0240] A comparison of Examples 2 and 8 shows that the ratio of the lithium-ion diffusion coefficient of the first region graphite to the lithium-ion diffusion coefficient of the second region graphite in Example 2 is 100, and the ratio of the lithium-ion diffusion coefficient of the third region graphite to the lithium-ion diffusion coefficient of the second region graphite in Example 2 is also 100. However, the ratio of the lithium-ion diffusion coefficient of the first region graphite to the lithium-ion diffusion coefficient of the second region graphite in Example 8 is 588, and the ratio of the lithium-ion diffusion coefficient of the third region graphite to the lithium-ion diffusion coefficient of the second region graphite in Example 8 is also 588. The significant difference in the ratios of the lithium-ion diffusion coefficients of the first and second regions graphite in Example 8, and the significant difference in the ratios of the lithium-ion diffusion coefficients of the third and second regions graphite in Example 8, results in the battery cell of Example 8 having fewer 80% SOC cycle times than the battery cell of Example 2.

[0241] As can be seen from Examples 9 to 12, the main body of the negative electrode sheet in Examples 9 to 12 is divided into a first region, a fourth region, a second region, a fifth region, and a third region, and the number of cycles at 80% SOC of the battery cell is 2160 to 2388.

[0242] A comparison between Comparative Example 1 and Example 1 shows that the main body of the negative electrode sheet in Comparative Example 1 has no divided regions, and the lithium-ion diffusion coefficient of the graphite in the entire negative electrode sheet is the same as that of the graphite in the first or third region of Example 1, which is 1.8*10. -11 Its battery cells have only 1316 cycles at 80% SOC.

[0243] A comparison between Comparative Example 2 and Example 1 shows that the main body of the negative electrode sheet in Comparative Example 2 has no divided regions, and the lithium-ion diffusion coefficient of the graphite in the entire negative electrode sheet is the same as that of the graphite in the second region of Example 1, which is 6.6*10. -12Its battery cells have only 989 cycles at 80% SOC.

[0244] A comparison between Comparative Example 3 and Example 1 shows that the negative electrode sheet of Comparative Example 3 has no defined regions, and the average lithium-ion diffusion coefficient of the graphite in the entire negative electrode sheet is the same as the average lithium-ion diffusion coefficient of the graphite in the first, second, and third regions of Example 1, which is 1.1*10. -11 Its battery cells have only 1229 cycles at 80% SOC.

[0245] It should be noted that this application is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments with the same structure and effect as the technical concept within the scope of this application are included in the technical scope of this application. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, without departing from the spirit of this application, are also included in the scope of this application.

Claims

1. A battery cell, characterized by, The battery cell comprises an electrode assembly, the electrode assembly comprises a negative electrode tab, the negative electrode tab comprises a main body part and a tab, the main body part has opposite first and second ends, the tab is arranged at the first end, the direction from the first end to the second end is the width direction of the negative electrode tab, the main body part comprises a first region, a second region and a third region distributed in sequence along the width direction, the lithium ion diffusion coefficient of the first region is greater than that of the second region, and / or the lithium ion diffusion coefficient of the third region is greater than that of the second region. The lithium ion diffusion coefficient in the first region and / or the third region is 10 -9 cm 2 / s~10 -11 cm 2 / s, and the lithium ion diffusion coefficient in the second region is 10 -11 cm 2 / s~10 -12 cm 2 / s.

2. The battery cell of claim 1, wherein, The ratio of the lithium ion diffusion coefficient of the first region to that of the second region is 2-1000, and / or the ratio of the lithium ion diffusion coefficient of the third region to that of the second region is 2-1000.

3. The battery cell of claim 1, wherein, The main body part is in sequence along the width direction of the first region, the second region and the third region, the ratio of the lithium ion diffusion coefficient of the first region and / or the third region to that of the second region is 5-500.

4. The battery cell of claim 1, wherein, The area of the second region accounts for 50%-70% of the total area of the main body part.

5. The battery cell of claim 4, wherein, The size ratio of the first region, the second region and the third region along the width direction is 15%-25%: 50%-70%: 15%-25%.

6. The battery cell of claim 1, wherein, The negative electrode tab comprises a negative electrode active material layer, the negative electrode active material layer comprises a negative electrode active material, the lithium ion diffusion coefficient of the negative electrode active material in the first region and / or the third region is greater than that of the negative electrode active material in the second region.

7. The battery cell of claim 1, wherein, The negative electrode tab comprises a negative electrode active material layer, the first region, the second region and the third region comprise the same conductive agent, the mass fraction of the conductive agent in the negative electrode active material layer in the first region is W1 based on the mass of the negative electrode active material layer in the first region, the mass fraction of the conductive agent in the negative electrode active material layer in the second region is W2 based on the mass of the negative electrode active material layer in the second region, and the mass fraction of the conductive agent in the negative electrode active material layer in the third region is W3 based on the mass of the negative electrode active material layer in the third region, W1W2 and / or W3W2.

8. The battery cell of claim 7, wherein, The difference between W2 and W1 is 0.5wt%-2wt%, and / or the difference between W2 and W3 is 0.5wt%-2wt%.

9. The battery cell of claim 1, wherein, The negative electrode tab comprises a negative electrode active material layer, the negative electrode active material layer comprises a conductive agent, the first region comprises a first conductive agent, the second region comprises a second conductive agent, and the third region comprises a third conductive agent, the electrical conductivity of the second conductive agent is greater than that of the first conductive agent, and / or the electrical conductivity of the second conductive agent is greater than that of the third conductive agent.

10. The battery cell of claim 1, wherein, The negative electrode tab comprises a negative electrode active material layer, the first region, the second region and the third region comprise the same binder, the mass ratio of the binder in the negative electrode active material layer in the first region is W4, the mass ratio of the binder in the negative electrode active material layer in the second region is W5 based on the mass of the negative electrode active material layer in the second region, the mass ratio of the binder in the negative electrode active material layer in the third region is W6 based on the mass of the negative electrode active material layer in the third region, W4>W5 and / or W6>W5.

11. The battery cell of claim 10, wherein, The difference between W4 and W5 is 0.5wt%-3.1wt%, and / or the difference between W6 and W5 is 0.5wt%-3.1wt%.

12. The battery cell of claim 1, wherein, The main body part further comprises a fourth region and a fifth region, the main body part comprises the first region, the fourth region, the second region, the fifth region and the third region which are sequentially distributed along the width direction, the lithium ion diffusion coefficient of the fourth region and / or the fifth region is greater than the lithium ion diffusion coefficient of the second region and less than the lithium ion diffusion coefficient of the first region.

13. The battery cell of claim 12, wherein, The size ratio of the first region, the fourth region, the second region, the fifth region and the third region along the width direction is 10%-15%:5%-10%:50%-70%:5%-10%:10%-15%.

14. The battery cell of claim 12, wherein, The ratio of the lithium ion diffusion coefficient of the fourth region and / or the fifth region to the lithium ion diffusion coefficient of the second region is 5-100.

15. The battery cell of claim 12, wherein, The lithium ion diffusion coefficient at the fourth region and / or the fifth region is 10 -10 cm 2 / s~5*10 -12 cm 2 / s.

16. A battery, characterized by The battery comprises the battery cell of any one of claims 1-15.

17. An electrical device, comprising: The power consuming device comprises the battery of claim 16, and the battery is used to provide electric energy.

Images